Power amplifier module

ABSTRACT

A power amplifier module includes a first bipolar transistor configured to amplify a radio frequency signal and output an amplified signal and a second bipolar transistor. A base of the second bipolar transistor is supplied with a control voltage for controlling attenuation of the radio frequency signal, and a collector the second bipolar transistor is supplied with a source voltage. The power amplifier module also includes a first resistor, where one end of the first resistor is connected to a supply path of the radio frequency signal to the first bipolar transistor, and a capacitor, where one end of the capacitor is connected to the other end of the first resistor and the other end of the capacitor is connected to the collector of the second bipolar transistor.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a power amplifier module.

Background Art

In a power amplifier module that amplifies a radio frequency (RF)signal, an attenuator may be provided to reduce the gain of the poweramplifier module in a low-power mode.

For example, Patent Document 1 discloses an attenuator that isshunt-connected to an input path of an RF signal to an amplificationtransistor. Specifically, the attenuator includes a field effecttransistor (FET) and realizes attenuation control by controlling avoltage applied to the gate of the FET so as to switch the ON/OFF stateof the FET.

CITATION LIST Patent Document

[Patent Document 1] JP 2012-134627 A

SUMMARY OF THE INVENTION

As disclosed in Patent Document 1, the attenuator can be embodied usingthe FET, but when a bipolar transistor is used as the amplificationtransistor, the bipolar transistor and the FET are mixed in the poweramplifier module, which causes an increase in the manufacturing cost.

The invention is made in consideration of the above-mentionedcircumstances and an object thereof is to provide a power amplifiermodule including an attenuator employing a bipolar transistor.

According to an aspect of the invention, there is provided a poweramplifier module including: a first bipolar transistor configured toamplify a radio frequency signal and output an amplified signal; asecond bipolar transistor, a base of the second bipolar transistor beingsupplied with a control voltage for controlling attenuation of the radiofrequency signal, and a collector the second bipolar transistor beingsupplied with a source voltage; a first resistor, one end of the firstresistor being connected to a supply path of the radio frequency signalto the first bipolar transistor; and a capacitor, one end of thecapacitor being connected to the other end of the first resistor, andthe other end of the capacitor being connected to the collector of thesecond bipolar transistor.

According to the invention, it is possible to provide a power amplifiermodule including an attenuator employing a bipolar transistor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a configuration of atransmitter unit including a power amplifier module according to anembodiment of the invention.

FIG. 2 is a diagram illustrating an example of a configuration of apower amplifier module.

FIG. 3 is a diagram illustrating another example of a configuration of apower amplifier module.

FIG. 4 is a diagram illustrating still another example of aconfiguration of a power amplifier module.

FIG. 5 is a diagram illustrating still another example of aconfiguration of a power amplifier module.

FIG. 6 is a diagram illustrating still another example of aconfiguration of a power amplifier module.

FIG. 7 is a diagram illustrating a configuration of a power amplifiermodule subjected to a simulation for current consumption.

FIG. 8 is a diagram illustrating a simulation result for currentconsumption.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an embodiment of the invention will be described withreference to the accompanying drawings. FIG. 1 is a diagram illustratingan example of a configuration of a transmitter unit including a poweramplifier module according to an embodiment of the invention. Atransmitter unit 100 is used to transmit various signals such as speechor data to a base station in mobile communication equipment such as amobile phone. The mobile communication equipment further includes areceiver unit that receives signals from the base stations, butdescription thereof will not be made herein.

As illustrated in FIG. 1, the transmitter unit 100 includes a basebandprocessing unit 101, a modulation unit 102, a power amplifier module103, a front end unit 104, and an antenna 105.

The baseband processing unit 101 performs baseband processing on aninput signal.

The modulation unit 102 modulates a baseband signal on the basis of amodulation method such as a global system for mobile communications(GSM®) method or an enhanced data GSM environment (EDGE) method andgenerates a radio frequency (RF) signal to be wirelessly transmitted.The frequency of the RF signal ranges, for example, from several hundredMHz to several GHz.

The power amplifier module 103 amplifies power of the RF signal (RFin)up to a level necessary for transmission to a base station and outputsthe amplified signal (RFout). The operating modes of the power amplifiermodule 103 include a low-power mode (LPM) and a high-power mode (HPM).The operating modes of the power amplifier module 103 are controlled bya control voltage Vctrl supplied from outside. As will be describedlater, in the power amplifier module 103, it is possible to reduce thegain of the power amplifier module 103 by operating an attenuator in thelow-power mode. In the power amplifier module 103, it may be possible toreduce the number of transistors operated (the number of fingers) in thelow-power mode.

The front end unit 104 performs filtering on the output signal,switching with a reception signal received from the base station, or thelike. The signal output from the front end unit 104 is transmitted tothe base station via the antenna 105.

FIG. 2 is a diagram illustrating an example of a configuration of thepower amplifier module 103. A power amplifier module 103A includes anamplifier 200 and an attenuator 210A. The transistors constituting thepower amplifier module 103A are bipolar transistors. For example, eachtransistor may employ a heterojunction bipolar transistor (HBT) of acompound semiconductor such as GaAs. In FIG. 2, the amplifier includesonly a single stage, but the power amplifier module 103 may includemulti-stage amplifiers. The same is true of other configurations to bedescribed later.

The amplifier 200 amplifies an input RF signal (RFin) and outputs anamplified signal (RFout). As illustrated in FIG. 2, the amplifier 200includes transistors 220 and 221, resistors 222 and 223, a capacitor224, an inductor 225, and a matching network (MN) 226.

The transistor 220 (the first bipolar transistor) is an amplificationelement that amplifies an RF signal (RFin). The RF signal (RFin) isinput to the base of the transistor 220 via the capacitor 224, and thecollector of the transistor 220 is supplied with a source voltage (forexample, a source voltage Vcc output from a regulator) via the inductor225. An amplified signal (RFout) obtained by amplifying the RF signal(RFin) is output from the collector of the transistor 220 via thematching network 226.

The transistor 221 is an element that supplies a bias voltage to thetransistor 220. The base of the transistor 221 is supplied with a biascontrol voltage Vbias for controlling a bias via the resistor 222. Thecollector of the transistor 221 is supplied with a source voltage (forexample, a battery voltage Vbat). The emitter of the transistor 221 isconnected to the base of the transistor 220 via the resistor 223.

The attenuator 210A serves to reduce the gain of the power amplifiermodule 103A. Specifically, the attenuator 210A can reduce the gain ofthe power amplifier module 103A by attenuating the RF signal (RFin)supplied to the transistor 220 in the low-power mode. As illustrated inFIG. 2, the attenuator 210A includes a transistor 230, resistors 231 to233, and a capacitor 234.

The transistor 230 (the second bipolar transistor) is an element that isturned on/off in response to the control voltage Vctrl to control theON/OFF states of an attenuation function. The base of the transistor 230is supplied with the control voltage Vctrl via the resistor 231. Thecollector of the transistor 230 is supplied with a source voltage (forexample, a battery voltage Vbat) via the resistor 232.

One end of the resistor 233 is connected to a supply path of the RFsignal (RFin) to the transistor 220 and the other end of the resistor233 is connected to one end of the capacitor 234. The other end of thecapacitor 234 is connected to the collector of the transistor 230. Theresistor 233 is an element that attenuates the RF signal (RFin) using acurrent flowing in the resistor 233 when the transistor 230 is turnedon. The capacitor 234 is a DC blocking element that prevents a DCcomponent of the collector of the transistor 230 from being supplied tothe supply path of the RF signal (RFin) to the transistor 220.

In the power amplifier module 103A illustrated in FIG. 2, the controlvoltage Vctrl is set to a high level in the low-power mode and is set toa low level in the high-power mode. When the control voltage Vctrl is atthe high level in the low-power mode, the transistor 230 is turned onand a part of the RF signal (RFin) flows into the transistor 230 via theresistor 233. Accordingly, the RF signal (RFin) is attenuated and thusthe gain of the power amplifier module 103A is reduced. On the otherhand, when the control voltage Vctrl is at the low level in thehigh-power mode, the transistor 230 is turned off, the RF signal (RFin)does not flow into the resistor 233, and thus the RF signal (RFin) issupplied to the transistor 220 without being attenuated.

In this way, in the power amplifier module 103A illustrated in FIG. 2,both of the amplifier 200 and the attenuator 210A can be constituted bybipolar transistors. Accordingly, it is possible to suppress themanufacturing cost of the power amplifier module, compared with the casein which the amplifier is constituted by a bipolar transistor and theattenuator is constituted by an FET.

FIG. 3 is a diagram illustrating another example of the configuration ofthe power amplifier module. The same elements as illustrated in FIG. 2will be referenced by the same reference numerals and descriptionthereof will not be repeated. As illustrated in FIG. 3, a poweramplifier module 103B includes an attenuator 210B instead of theattenuator 210A in the power amplifier module 103A illustrated in FIG.2. The attenuator 210B includes a transistor 300 in addition to theelements of the attenuator 210A.

The base of the transistor 300 (the third bipolar transistor) isconnected to the collector of the transistor 300, the collector of thetransistor 300 is connected to the emitter of the transistor 230, andthe emitter of the transistor 300 is grounded. That is, the transistor300 is a diode-connected transistor and is connected to the ground sideof the transistor 230. In this way, by disposing the diode-connectedtransistor 300 on the ground side of the transistor 230, it is possibleto reduce the base-emitter voltage of the transistor 230 and thus toreduce a DC current (that is, a current 12 flowing in the resistor 232)flowing in the transistor 230 in the low-power mode.

FIG. 4 is a diagram illustrating still another example of theconfiguration of the power amplifier module. The same elements asillustrated in FIG. 2 will be referenced by the same reference numeralsand description thereof will not be repeated. As illustrated in FIG. 4,a power amplifier module 103C includes an attenuator 210C instead of theattenuator 210A in the power amplifier module 103A illustrated in FIG.2. The attenuator 210C includes a transistor 400 and resistors 401 to403 in addition to the elements of the attenuator 210A.

The base of the transistor 400 (the fourth bipolar transistor) issupplied with the control voltage Vctrl via the resistor 401. Thecollector of the transistor 400 is supplied with the source voltage (forexample, the battery voltage Vbat) via the resistor 402 (the secondresistor) and the resistor 403 (the third resistor). The base of thetransistor 230 is connected to a connecting point of the resistors 402and 403 via the resistor 231.

In the power amplifier module 103C, unlike the power amplifier module103A illustrated in FIG. 2, the control voltage Vctrl is set to a lowlevel in the low-power mode and is set to a high level in the high-powermode. That is, the attenuation function of the attenuator 210C is turnedon when the control voltage Vctrl is at the low level, unlike theattenuator 210A illustrated in FIG. 2.

When the control voltage Vctrl is at the low level in the low-powermode, the transistor 400 is turned off, the battery voltage Vbat issupplied to the base of the transistor 230, and thus the transistor 230is turned on. Accordingly, a part of the RF signal (RFin) flows into thetransistor 230 via the resistor 233 and the RF signal (RFin) isattenuated.

On the other hand, when the control voltage Vctrl is at the high levelin the high-power mode, the transistor 400 is turned on. At this time,the base of the transistor 230 is supplied with a voltage, which isobtained by dividing the battery voltage Vbat by the use of theresistors 402 and 403, via the resistor 231. That is, the voltagesupplied to the base of the transistor 230 decreases and the transistor230 is turned off. Accordingly, the RF signal (RFin) does not flow intothe resistor 233 and the RF signal (RFin) is supplied to the transistor220 without being attenuated.

In this way, in the power amplifier module 103C, the low-power mode canbe set up when the control voltage Vctrl is at the low level. That is,the power amplifier module 103C can be suitably applied to a transmittermodule in which the control voltage Vctrl is designed to the low levelin the low-power mode.

FIG. 5 is a diagram illustrating still another example of theconfiguration of the power amplifier module. The same elements asillustrated in FIG. 4 will be referenced by the same reference numeralsand description thereof will not be repeated. As illustrated in FIG. 5,a power amplifier module 103D includes an attenuator 210D instead of theattenuator 210C in the power amplifier module 103C illustrated in FIG.4. The attenuator 210D includes transistors 500 and 501 in addition tothe elements of the attenuator 210C.

The base of the transistor 500 (the fifth bipolar transistor) isconnected to a connecting point of the resistors 402 and 403 via theresistor 231. The collector of the transistor 500 is supplied with thesource voltage (for example, the battery voltage Vbat) via the resistor232. The emitter of the transistor 500 is connected to the base of thetransistor 230. That is, the transistors 230 and 500 form a Darlingtontransistor.

The base of the transistor 501 (the sixth bipolar transistor) issupplied with the control voltage Vctrl via the resistor 401. Thecollector of the transistor 501 is supplied with the source voltage (forexample, the battery voltage Vbat) via the resistors 402 and 403. Theemitter of the transistor 501 is connected to the base of the transistor400. That is, the transistors 400 and 501 form a Darlington transistor.

The operation of the attenuator 210D is the same as the attenuator 210Cillustrated in FIG. 4. That is, when the control voltage Vctrl is at thelow level in the low-power mode, the transistors 400 and 501 are turnedoff and the transistors 230 and 500 are turned on, thereby performingthe attenuation of the RF signal (RFin). On the other hand, when thecontrol voltage Vctrl is at the high level in the high-power mode, thetransistors 400 and 501 are turned on and the transistors 230 and 500are turned off, thereby not performing the attenuation of the RF signal(RFin).

In the attenuator 210D, since the transistors 400 and 501 form aDarlington transistor, it is possible to reduce the base current 13flowing in the resistor 401, compared with the attenuator 210C.

In the attenuator 210D, since the transistors 230 and 500 form aDarlington transistor, a threshold voltage for turning on thetransistors 230 and 500 is higher than the threshold voltage for turningon the transistor 230 in the attenuator 210C. Accordingly, particularly,when the signal level of the RF signal (RFin) is high, it is possible topreventing a leakage current from flowing in the transistor 230 in thehigh-power mode, compared with the attenuator 210C.

FIG. 6 is a diagram illustrating still another example of theconfiguration of the power amplifier module. The same elements asillustrated in FIG. 3 or 5 will be referenced by the same referencenumerals and description thereof will not be repeated. As illustrated inFIG. 6, a power amplifier module 103E includes an attenuator 210Einstead of the attenuator 210D in the power amplifier module 103Dillustrated in FIG. 5. The attenuator 210E includes the transistor 300illustrated in FIG. 3 instead of the transistor 500 in the attenuator210D. Similarly to the attenuator 210B illustrated in FIG. 3, thetransistor 300 is a diode-connected transistor and is disposed on theground side of the transistor 230.

FIG. 7 is a diagram illustrating a configuration of a power amplifiermodule subjected to a simulation for current consumption. As illustratedin FIG. 7, a power amplifier module 103F includes two-stage amplifiers200A and 200B and an attenuator 210. The amplifiers 200A and 200B havethe same configuration as the amplifier 200 illustrated in FIGS. 2 to 6.The simulation is carried out on the configurations employing theattenuators 210A to 210E illustrated in FIGS. 2 to 6 as the attenuator210. In the simulation, the number of fingers of the transistor 220constituting the amplifier 200B is set to 16 and the number of fingersoperated is reduced to 12 in the low-power mode.

FIG. 8 is a diagram illustrating the simulation results for the currentconsumption. Currents I1 to I4 are sequentially currents flowing in theresistors 231 and 232 and the resistors 401 and 403 of the attenuators210A to 210E illustrated in FIGS. 2 to 6. In the table illustrated inFIG. 8, values A to E in the column of the attenuator correspond to theattenuators 210A to 210E. As illustrated in FIG. 8, in anyconfiguration, the gain in the low-power mode is about 20 dB and thegain in the high-power mode is about 25 dB.

Comparing the attenuator 210A with the attenuator 210B, it can be seenthat the current consumption in the attenuator 210B is lower. Asdescribed above, this is because the diode-connected transistor 300 isdisposed on the ground side of the transistor 230 in the attenuator 210Band thus the current I2 is reduced.

Comparing the attenuator 210C with the attenuator 210D, it can be seenthat the current consumption in the low-power mode of the attenuator210D is lower. As described above, this is because the transistors 400and 501 in the attenuator 210D form a Darlington transistor.

Hitherto, embodiments of the invention have been described. According toone embodiment, both of the amplifier 200 and the attenuator 210 can beconstituted by bipolar transistors. Accordingly, it is possible tosuppress the manufacturing cost of the power amplifier module, comparedwith the case in which the amplifier is constituted by a bipolartransistor and the attenuator is constituted by an FET.

According to another embodiment, it is also possible to reduce thecurrent consumption by disposing the diode-connected transistor 300 onthe ground side of the transistor 230, as illustrated in FIG. 3.

According to another embodiment, it is also possible to perform controlso as to turn on the attenuation function when the control voltage Vctrlis at the low level, by disposing the transistor 400 and the resistors401 to 403, as illustrated in FIG. 4.

According to another embodiment, it is also possible to reduce thecurrent consumption by the Darlington transistor formed from transistors400 and 501, as illustrated in FIG. 5. By forming a Darlingtontransistor comprising the transistors 230 and 500, it is possible toprevent a leakage current from flowing in the transistor 230 when thesignal level of the RF signal (RFin) is high.

According to another embodiment, it is also possible to reduce the powerconsumption by disposing the diode-connected transistor 300 on theground side of the transistor 230, as illustrated in FIG. 6.

The embodiments are for easy understanding of the invention, but not forrestrictively analyzing the invention. The invention can bemodified/improved without departing from the gist thereof andequivalents thereof are included in the invention.

DESCRIPTION OF REFERENCE NUMERALS

-   -   100: transmitter unit    -   101: baseband processing unit    -   102: modulation unit    -   103: power amplifier module    -   104: front end unit    -   105: antenna    -   200: amplifier    -   210: attenuator    -   220, 221, 230, 300, 400, 401, 500, 501: transistor    -   222, 223, 231 to 233, 401 to 403: resistor    -   224, 234: capacitor    -   225: inductor    -   226: matching network

What is claimed is:
 1. A power amplifier module, comprising: a firstbipolar transistor configured to amplify a radio frequency signal andoutput an amplified signal; a first terminal to which a control voltagefor controlling attenuation of the radio frequency signal is supplied; asecond terminal to which a source voltage is applied; a second bipolartransistor, a base of the second bipolar transistor being supplied withthe control voltage through the first terminal, and a collector of thesecond bipolar transistor being supplied with the source voltage throughthe second terminal; a first resistor and a capacitor that are seriallyconnected and provided between a supply path of the radio frequencysignal to the first bipolar transistor; and a third bipolar transistor,a base of the third bipolar transistor being connected to a collector ofthe third bipolar transistor, and the collector of the third bipolartransistor being connected to an emitter of the second bipolartransistor.
 2. The power amplifier module according to claim 1, furthercomprising: a second resistor; a third resistor connected in series tothe second resistor; a fourth bipolar transistor, a collector of thefourth bipolar transistor being supplied with the source voltage via thesecond and third resistors; and a sixth bipolar transistor, a base ofthe sixth bipolar transistor being supplied with the control voltage, acollector of the sixth bipolar transistor being connected to thecollector of the fourth bipolar transistor, and an emitter of the sixthbipolar transistor being connected to the base of the fourth bipolartransistor, wherein the base of the second bipolar transistor isconnected to a connecting point of the second and third resistors. 3.The power amplifier module according to claim 1, wherein each of thefirst bipolar transistor, the second bipolar transistor, and the thirdbipolar transistor is a transistor of a compound semiconductor.
 4. Thepower amplifier module according to claim 2, wherein each of the firstbipolar transistor, the second bipolar transistor, the third bipolartransistor, the fourth bipolar transistor, and the sixth bipolartransistor is a transistor of a compound semiconductor.
 5. The poweramplifier module according to claim 1, wherein the first bipolartransistor configured to amplify a radio frequency signal and output anamplified signal is part of a multi-stage amplifier.
 6. The poweramplifier module according to claim 2, wherein the first bipolartransistor configured to amplify a radio frequency signal and output anamplified signal is part of a multi-stage amplifier.